The present invention relates to a semiconductor device and a method of manufacturing the same and is, for example, suitably applicable to a semiconductor device including a field-effect transistor having a thick insulating film in a trench of a substrate surface between a drain and a source.
To be in use for an LDMOSFET (Laterally Diffused Metal-Oxide-Semiconductor Field Effect Transistor, LDMISFET: hereafter, simply referred to as an “LDMOS”), an RESURF (REduced SURface Field) type MOS transistor is adopted as a commonly used configuration. Besides this, there is studied a configuration which alleviates a magnetic field intensity under a drain side edge of a gate electrode by forming a thick oxide film over a surface of a semiconductor substrate and arranging the drain side edge of the gate electrode over the oxide film.
For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2014-107302) discloses an example in which, when arranging part of a gate electrode of an LDMOS over an element isolation region having an STI (Shallow Trench Isolation) structure, an opening penetrating the gate electrode is formed in a semiconductor substrate between the element isolation region and a source region.